Non-contacting mechanical face seal

ABSTRACT

Improved spiral grooves in a mechanical face seal have plural terminal corners which more evenly distribute the fluid pressure generated within the seal gap into discrete pressure zones which are radially displaced and may also be circumferentially displaced from the other pressure zones generated by the same groove. Alternative embodiments include grooves having surfaces of varying depths wherein each of the plural terminal groove corners is associated with a section of the groove having a surface at a particular depth.

CROSS REFERENCES TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 08/101,589, filed on Aug.3, 1993, now U.S. Pat. No. 5,441,283.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to rotary mechanical end face seals andmore particularly to rotary mechanical end face seals having spiralgrooves for creating a fluid gap between the sealing faces.

2. Background Art

Mechanical face seals long have been used for sealing between a housingand a relatively rotating shaft. More recently, grooves have beenintroduced into the sealing face of at least one of the sealing rings tohelp generate a gap between the seal faces, which gap separates therings. These type of seals are generally referred to as non-contactingseals. Spiral grooves have been utilized for pumping fluid between theseal faces so that the fluid creates a small gap between the facesduring shaft rotation. Examples of spiral grooved faces are found inU.S. Pat. No. 3,499,653 and in U.S. Pat. No. 4,212,475, both of whichare commonly assigned with the present invention and the teachingsthereof which are incorporated herein by reference.

The spiral grooves heretofore disclosed comprise two generally smoothboundary curves which separate the grooved area from the land. These twoboundary curves are essentially parallel to each other and eachterminate at end points disposed essentially at the same radial distancefrom the centerline of the seal face. These two end points are joined bya transverse boundary which, for the most part, extends in thecircumferential direction to produce the spiral groove patterns shown inFIG. 2 of each of U.S. Pat. Nos. 3,499,653 and 4,212,475.

It has been found that spiral grooves of the prior art seals areeffective for providing a gap between the seal faces. Nevertheless,these types of seal face patterns have characteristics that result fromthe shape of the grooves. The shape of the grooves includes a singleterminal corner at the point where the trailing boundary of the grooveintersects a circumferential boundary of the groove to provide an acuteangle at the intersection point. The angle is located between the twocircumferential edges of the sealing face and is referred to herein as aterminal corner.

The single terminal corner design results in a pressure "zone" that iscreated adjacent the terminal corner of each groove. For the set ofgrooves in a standard spiral groove seal face, one such zone is producedby each groove. It is thought that this pressure zone occurs at a spoton the land immediately adjacent the groove terminal corner, and morespecifically, at the edge of the land opposite the direction in whichthe seal face is relatively rotating and on the other side of theboundary line between the groove and land from the groove. The pressurebuildup at this point is thought to occur because of the convergingfluid mass flow into the terminal corner which occurs from theconverging trailing and circumferential boundaries of the groove at theintersection point. In the conventional spiral groove sealing face, thepressure zones associated-with each groove are thus each disposed atapproximately the same radial position relative to the shaft centerlinebut are circumferentially displaced at or immediately adjacent theboundary line between the grooved portion and the ungrooved portion ordam.

The creation of a limited number of pressure zones, necessarily limitedby the one-to-one relationship with each of the standard spiral grooves,is sufficient to provide enough lift to separate the faces of amechanical face seal and to create the gap therebetween. In the spiralgrooves of U.S. Pat. No. 3,499,653 and of U.S. Pat. No. 4,212,475, thenumber of pressure zones are limited to the total number of spiralgrooves which are present in the seal face, and these are arranged atessentially identical radii along a circumferential line approximatelyadjacent the boundary between the grooved portion and the dam.

SUMMARY OF THE INVENTION

This invention discloses a mechanical face seal for providing a sealbetween a pair of relatively rotatable components comprising a firstseal ring adapted to be mounted non-rotatably on one component andsealed with respect thereto, a second seal ring adapted to be mountednon-rotatably on the other component and sealed with respect to theother component, the second seal ring being mounted in axial alignmentwith the first seal ring, and means being provided for resilientlyurging a sealing face of the first seal ring axially into sealingengagement with a sealing face of the second seal ring, the sealing faceof one of the seal rings having an annular grooved area disposed aroundits circumference, the grooved area opening to one edge of the sealingface, a continuous annular dam formation being provided between thegrooved area and the other edge of the sealing face, the grooved areahaving: a plurality of grooves angularly disposed and extending radiallyand circumferentially in a given direction partially across the sealingface from one circumferential edge of the sealing face toward the othercircumferential edge, each groove having at least two boundaries, eachboundary extending generally radially and circumferentially, and one ofthe boundaries having plural terminal corners as further defined herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a seal face having a spiral groove face pattern according tothe present invention.

FIG. 2 is a cross-sectional view of a portion of the seal face of FIG. 1taken approximately along the line 2--2.

FIG. 3 is another embodiment of the seal face pattern according to thepresent invention.

FIG. 4 is a cross-sectional view of a portion of the seal face of FIG. 3taken approximately along line 4--4.

FIG. 5 shows another embodiment according to the present invention.

FIG. 6 shows a cross-section of a portion of the seal face of FIG. 5taken approximately along a line 6--6.

FIG. 7 shows a cross-sectional view of an alternative embodiment of theseal face illustrated in FIGS. 5 and 6.

FIG. 8 shows another embodiment according to the present invention.

FIG. 9 illustrates still another embodiment according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a seal ring 10 having a generally radially extendingseal face 12 which is shaped and dimensioned to oppose the face onopposing seal face of a second ring (not shown). The seal ring 10 may beeither a primary or a mating ring, and may either rotate with the shaft(not shown) or be sealingly connected to the housing (not shown) as isexplained in the aforementioned U.S. Pat. No. 3,499,653 and U.S. Pat.No. 4,212,475. The seal face 12 has a discrete pattern of groovedsurfaces and ungrooved surfaces as do the seal faces of theaforementioned patents. An annular grooved portion 14 is adjacent one ofthe circumferential edges of the seal ring 10 and another annular dam 16is at the other of the circumferential edges. In the embodiment of FIG.1, the annular grooved surface 14 is adjacent the outer diametercircumferential edge 18 of the seal ring 10. However, as in the sealrings of the aforementioned patents, the annular grooved surface mayextend from either the outer diameter edge 18, as is shown, or from theinner diameter edge of the seal ring, depending on the design of themechanical end face seal.

The annular grooved surface 14 further comprises a plurality of grooves20 which are evenly spaced around the periphery of the annular groovedportion 14. Lands 22 separate adjacent ones of the grooves 20. Thegrooves 20 are similar in many respects with the grooves of theaforementioned patents in having as a boundary one of thecircumferential edges, such as edge 18, of the seal ring face 12. Atleast two other boundaries define each groove 20, a first grooveboundary 21 which extends both circumferentially and radially and asecond jagged groove boundary 23, which also extends circumferentiallyand radially. However, in the inventive seal, one of thecircumferentially and radially extending boundaries 21,23 of grooves 20includes plural terminal corners 24. These corners 24 provide a numberof advantages as will be discussed below.

The plural terminal corners 24 are each formed in one of the twoboundaries 21,23. The boundary, for example 23, preferably comprises asequential series of circumferentially extending edges, such as edges26, joined to each other by a series of second edges 28, which extendboth circumferentially and radially. Each of the terminal corners 24 areformed by an adjacent pair of converging edges 26,28. The boundary (23)with the terminal corners 24 also generally extends in the radialdirection, and may extend circumferentially in the same generaldirection as the other boundary (21).

The boundary which provides the leading edge of the groove 20 when theseal ring 10 rotates in the intended direction, as shown by the arrow,is referred to as the leading edge boundary and is indicated by 21 inFIG. 1. The leading edge boundary 21 is the first part of a groove 20which passes a theoretical stationary point located directly over thesealing face 12. The leading edge boundary defines an acute angle e withthe circumferential edge 18, as shown in FIG. 1. In the preferredembodiment, the angle α is approximately 19° but may take on othervalues in a range of from 5° to about 85° depending on the design of theseal and on other seal parameters, such as shaft rotational speed. Theleading edge boundary 21 is also generally convergent with the trailingedge 28 that intersects the circumferential edge 18 when both edges21,28 are extrapolated.

The structure of each groove 20 may be considered to comprise severaladjacent grooves, of the type described in U.S. Pat. No. 4,212,475,which have differing lengths and have been joined together withoutintervening lands between them. One of the boundaries 21 or 23 followsthe same path as would a leading edge boundary of a conventional spiralgroove. The other boundary, indicated by 23 in FIG. 1, includes distinctcorners 24 having ending points which are disposed along the boundary 23and which are formed by adjacent converging edges 26,28. These endingpoints, referred to herein as terminal corners 24, are preferablydisplaced both in the radial and in the circumferential directions fromother adjacent terminal corners of the same groove, as shown.Nevertheless, grooves with terminal corners which may be aligned along acommon radius can also operate effectively.

The number of grooves 20 around the periphery of the annular groovesurface 14 may be in a range of from two to sixty depending on the sizeof the seal face and of the outer diameter of the seal ring 10. Thegrooves 20 should be evenly spaced about the annular grooved area 14 ina radially symmetric pattern.

A land to groove ratio from one to three to one to five is preferred.The land to groove ratio, as defined herein, is the ratio of thecircumferential width of the land 22 as compared to the groove 20. Thecircumferential width is the linear dimension of the circumscribing arctaken at the circumferential edge 18. The land to groove ratio iscalculated by taking the arc bounding the land 22 in relation to thatbounding the groove 20, both taken at the circumferential edge 18. Thespecific ratio will depend on the design of the mechanical seal withwhich these seal ring faces are used and may vary significantly from aone to three through one to five ratio depending on seal design.

Preferably, the number of terminal corners 24 which are associated withthe jagged boundary 23 of each groove 20 may range from two to tendepending on the width of the face and on the size of the ring. Thegroove depths may have a preferred range of from 25 to 2000 microinches,as is desired for specific uses of the seal ring.

During seal operation, as the shaft and seal face rotate, the fluid ispumped into the gap between the seal faces and the fluid must flow overthe intersection point of each corner 24 formed by the associated edges26,28. The fluid flow-inhibiting obstacle presented at the terminalcorner 24 by the increase in surface height at the boundary 23 betweenthe groove 20 and land 22 must be overcome. The volume in which thefluid is forced into by the converging edges 26,28 becomes constrictedas the fluid reaches the terminal corner intersection point 24. Thevolume constriction and concentration of fluid into a smaller arearaises the pressure of that fluid at or adjacent the point 24 and, as itflows over that intersection point, a pressure "zone" 25, shown inphantom, is created in the gap between the seal faces immediatelyadjacent the terminal corner 24.

To further aid in the constriction of volume available to the fluid, theleading edge boundary 21 is also preferably convergent with the boundary23 and edges 28, which edges 28 also extend both radially andcircumferentially. The boundary 21 is not shown to intersect with edges28 in FIG. 1; it is contemplated that extrapolated extensions of theedges (not shown) could intersect at a point somewhere on the face 12 ofthe seal ring 10.

Since one of these pressure "zones" 25 are each associated with one ofthe groove terminal corners 24, the pressure zones are disposed acrossthe seal face grooved area portion 14 following the pattern of theterminal groove corners in both the radial and circumferentialdirections in the general shape of a spiral. A seal face pattern havingmultiple pressure "zones", which are both circumferentially and radiallydisposed relative to each other, are considered to provide a moreefficient bearing surface and a stiffer fluid film in the gap than thoseof a conventional spiral groove pattern. Moreover, the multiplicity ofpressure "zones" bearing the seal faces minimizes the variation in thegap, and minimizes thermal differentials which would normally be causedby a single large pressure "zone", such as is produced by the spiralseal face patterns-of the aforementioned U.S. patents. The greaternumber of terminal corners 24 associated with each groove 20, ascompared to conventional grooves, provides the advantage of more stable"lift" between the seal faces when the shaft rotates and the groovespump fluid between the sealing faces. The added lift derives from themultiple pressure zones which are associated with each groove 20 at oradjacent the adjacent terminal corners 24. The staggering of theterminal corners 24, and the associated pressure zones, distributes abroader base of pressure over the seal face grooved portion 14. Althoughbroader distribution of pressure zones reduces somewhat the amount ofpressure generated by each terminal corner 24, staggering of thepressure zones over several terminal corners 24 increases the stiffnessof the fluid film between the seal faces as that teem is conventionallydefined in, for example, U.S. Pat. No. 4.,212,475.

Furthermore, despite the relative reduction in the amount of pressure ateach pressure zone 25, the opening force of the grooves 20 is the sameas, if not greater than, the opening force which results from thegrooves of a conventional spiral groove pattern. If considered as anarray of two-dimensional springs, the conventional spiral groove willhave pressure zones or "springs" providing opening force to create theseal gap in a single circular pattern, each disposed at a common radius.These "springs" can be given an arbitrary force value of 3 which dependspartly on the amount of fluid mass flow across the terminal corner ofeach groove.

For a seal face 12 according to the embodiment of FIG. 1, the sameamount of mass flow of fluid being pumped by each groove produces threeseparate pressure zones 25, or "springs" for each groove 20, and eachpressure zone provides an opening force having a comparable value of 1.The total opening force provided by the seal face is the same orpossibly greater, since at lower pressures there is less tendency todeviate from a direct correlation between pressure at each zone and theopening force generated by that zone. Furthermore, the distribution ofthe opening force about a greater area of the seal face 12 has addedstabilization advantages, as will be described below.

The decreased amount of distributed pressure at any single groove cornerpressure zone 25 also tends to permit formation of a somewhat smallergap between the seal faces, thus resulting in less leakage. The gapbetween the seal faces may be controlled for a specific seal design byaltering some of the other parameters of the seal ring face, such asland to groove ratio, groove depths and/or angle of incidence of theleading or trailing edges. A smaller gap having a higher fluid stiffnessis more stable due to the reactive opening force tending to re-open thegap if one of the rings is skewed slightly causing the gap width toclose momentarily. That is, because some of the terminal corners 24 aredisposed much closer to the outer diameter of the seal face, a greatermoment arm is experienced. Thus, an upset in the parallel relationbetween the seal ring faces is counteracted by the angular dimension ofthe opening force, which because of the "leverage" provided by thelarger moment arm, tends to act sooner on the seal ring than would aconventional groove seal ring.

The more immediately counteracting force also may be attributable to thesmaller initial gap and increased fluid stiffness, which act morequickly to "right" the seal ring following an upset condition fromparallel. Also, the pressure buildup at each of the pressure zones thatare distributed radially across the seal face are all "compressed"together so that the plurality of pressure zones act as a "planar arrayspring" which has much less elasticity than would a conventional sealring face, in which a "circular array" of springs are counteracting theclosing force.

Still another advantage of the inventive seal face grooves 20 also is aresult of the decreased pressure at each individual terminal corner 24resulting from the distribution of the pressure generated by eachindividual groove 20. Continual pressure of the flowing fluid at apressure zone 25 develops an increase in temperature at an area on thering face immediately adjacent each terminal corner 24, and at about thesame location as that indicated by the pressure zones 25. The increasesin seal ring face temperature at these local areas createdisproportionate variations in temperature as measured at differentlocal areas of the seal face.

A corresponding higher temperature annular "band" also forms on theopposing seal ring face which results from the pressure zonescontinually passing over the same annular area on the opposing sealingface. The temperatures reached on the opposing seal face are not nearlyas high as those generated on the grooved seal ring face because thepressure zones 25 are moving relative to a localized area on theopposing sealing face.

Decreased pressure of any one pressure zone 25 necessarily reduces thetemperature which is developed by the pressure zone at any one localarea. Thus, the temperature gradient taken over the full seal face widthis reduced, and the increase in the temperature is distributed over anumber of local areas separated from each other, each at a lowerrelative temperature. This further develops a greater uniformity oftemperature across the seal face 14, because the temperature is moreconstant when measured across a greater radial swath of the seal ringface 12. Both reduced temperature gradient and the greater temperatureuniformity minimize thermal taper or "warping" of the seal rings, whichprovides for even greater stability in the gap between the seal facesduring shaft rotation.

FIGS. 3 and 4 show that variable groove depths may be used to provide acustomized, evenly distributed pressure zone profile for specific seals.For example, in FIG. 3, the grooves 40 are separated by lands 42. Thelands 42 are at the same height as the dam 36. However, each of thegrooves 40 may comprise, for example, three separate surfaces 44,46,48having varying depths within each groove 40. FIG. 4 more clearlyillustrates the three different surfaces at different depths. Theradially outermost section has a surface 44 which is indicated in FIGS.3 and 4 as the groove section closest to the circumferential edge 38 ofthe seal face 30. Surface 44 is at the greatest depth relative to theother two surfaces 46 and 48. An intermediate section has a surface 46at an intermediate depth and the innermost section has a surface 48which is at the shallowest depth.

As shown in FIG. 3, the surfaces of sections 44, 46 are separated by acircumferentially extending line 45; between section surfaces 46 and 48,there is a circumferentially extending boundary 47. Thus, a steppedgroove pattern is created by separate circumferentially extending groovesurfaces having different depths depending on the radial locationswithin the same groove 40.

The fluid experiences increasing height of the surfaces 44,46,48 as itis pumped further toward the terminal corners 54. The increasing heightin passing from a section having deeper surface to a section having ashallower surface further constricts the volume in which the fluid ispumped, and necessarily changes the characteristics of the pressure"zone" 55.

The grooves 60 of FIGS. 5 and 6 are similar to the embodiment of FIGS. 3and 4 in having the variation in the groove depths of surfaces ofdifferent sections of the groove 60 relative to the surface of the lands62. However, the different groove sections having surfaces 64, 66, and68 extend both radially and circumferentially so that the boundaries65,67 between the section surfaces 66 and 68 may extend parallel to theleading edge boundary 61. The boundary 67 may also extend colinearlywith the groove edge 72 which extends both circumferentially andradially.

In the embodiment shown in FIG. 5, and as best seen in FIG. 6, thelongest extending groove section 68 extends from the outer diameter 78to a terminal corner 74 which is closest to the inner diameter of theseal face. The surface 68 is also the deepest relative to the lands 62.The shortest groove section 64 located closest to the trailing edge 72which intersects the circumferential edge 78 also has the shallowestsurface. The intermediate groove section surface 66 is disposed betweensurfaces 64 and 68 and is at an intermediate depth between the surfacesof the two groove sections 64,68.

During operation of the seal having a seal ring face with grooves 60 asdescribed above, the seal ring 10 will preferably rotate with the shaft(not shown). As has been mentioned elsewhere, it is possible that theseal ring with the grooves 60 is stationary and the opposite ring (notshown) is rotating relative to the stationary ring. The important thingis that the rings are rotating relative to each other and the relativerotation provides a pumping action of fluid from one seal facecircumference at least partially across the seal face toward the othercircumference.

In the preferred method of operation, the seal ring is rotating togetherwith the shaft (not shown). As the ring rotates counterclockwise, asindicated in the FIG. 5 embodiment by the arrow, fluid is pumpedinwardly by the radially extending groove adjacent the outer edge 78. Asthe fluid is pumped inwardly it is also being directed toward one of theplural corners 74 by the convergence of the edges 72,76 forming each ofthe plural corners 74. The increasing height between the sectionsurfaces 64,66,68 further constricts the volume available for fluid inthe terminal corners 74 closer to the outer circumferential edge 78 ofthe seal face. The converging edges and the increasing height of thesurfaces together cause the pressure of the fluid being pumped inwardlyto create one pressure zone immediately adjacent each of the pluralcorners 74. Moreover, the variance in height of each section surface64,66,68 compensates for the decrease in length of those sections closerto the trailing boundary edge 63 of the grooves 60.

FIG. 7 is a cross-sectional view of an alternative embodiment to thatshown in FIGS. 5 and 6. The general shape of the seal face 62',including the different groove depths of each of the section surfaces64, 66, 68, are essentially the same as in the seal face of FIG. 5, andthus these surfaces in FIG. 7 will be designated by a prime as sectionsurfaces 64', 66' and 68'. Other elements of the embodiment of FIG. 7which are essentially identical to the embodiment of FIGS. 5 and 6, suchas circumferential edge 78', will also be indicated by a prime.

The seal ring 60' has a seal face in which lands 62' separate groovedareas which have surfaces 64', 66', 68' at different heights to eachother relative to the lands 62'. In addition, the boundaries 65', 67'between the separate groove surfaces 64', 66'and 68'further comprisemicrodams 102, such as are disclosed in U.S. Pat. No. 5,090,712,commonly invented and assigned to a common assignee as this invention.The teachings of microdams in that patent are incorporated herein byreference, where appropriate.

Microdams 102 follow the boundaries 65', 67', which define the samegeneral spiral shape as do boundaries 65, 67 of FIGS. 5 and 6. Themicrodams 102 are at the same height as the lands 62' and form a "wall"between the separate groove section surfaces 64', 66', 68'. Preferably,the microdams have a width in the range of from 0.001 to about 0.100inches and are preferably each 0.0025 inches wide. The microdams 102, ineffect, separate the section surfaces into separate grooves that aredisposed adjacent each other. The function performed by these microdams102 is thought to be an isolation of the different groove sections sothat the fluid which is being pumped into the volume defined by eachsection surface 64', 66', 68' is effectively isolated from the fluidbeing pumped into the neighboring volumes. It is considered that theisolation function more evenly distributes the pumped fluid between eachof the volumes of the associated section surfaces, thus betterequalizing the amount of fluid mass flow being pumped into each corner74'.

FIG. 8 illustrates yet another embodiment of the present invention whichhas a seal ring 80 with a greater number of grooves disposed on thesealing face 82 for creation of a greater number of pressure zones. Thegroove area 84 is annularly shaped. The annular dam 86 of seal ring 80may be identical to the dam 16 of the embodiment of FIG. 1. The annulargrooved area 84 is bounded at one annular circumference by the boundarybetween the dam 86 and the grooved area 84, and at the other annularcircumference by grooved area 84, and at the other annular circumferenceby one circumferential edge 88 of the seal ring 80, whether the innerdiameter edge or the outer diameter edge as shown.

The annular grooved area 84 comprises grooves 90 which are evenlydisposed around one circumference of the sealing face 82. The grooves 90are separated by lands 92 disposed between adjacent grooves 90. Thecircumferential edge 88 serves as one boundary of each groove 90. Atleast two other boundaries, a leading edge boundary 91 and a trailingedge boundary 93 also define the shape of each groove 90. Bothboundaries 91 and 93 extend from the one sealing face circumferentialedge 88 toward the other generally in circumferential and radialdirections. As in the other embodiments, the trailing edge boundary 93includes several edges, a pair of which define each plural terminalcorner 94. These edges may be both circumferentially extending edges 96in conjunction with circumferentially and radially extending edges 98.

The difference between the groove shape of the grooves 20 in theembodiment of FIG. 1 and the shape of groove 90 in the embodiment ofFIG. 8 to some extent is found in the angle of incidence of the leadingedge boundary 91 relative to the sealing face circumferential edge 88.The leading boundary 21 of the grooves 20 (FIG. 1) intersects the edge18 at a more acute angle than does the corresponding angle of theembodiment of FIG. 8. The greater angle of incidence does not detractappreciably from the pumping capability of the grooves 90, but doesprovide the benefit that each groove 90 extends for a much shortercircumferential distance along circumferential edge 88. That is, theboundary of the groove 90 along the circumferential edge 88circumscribes a significantly shorter arc than the similar boundary ofthe groove 20. This permits a greater number of grooves 90 to bedisposed on sealing face 82, eighteen as shown in FIG. 8, compared tothe ten grooves shown in the sealing face 12 of seal ring 10 (FIG. 1).

The trailing edge boundary 93 is further defined by the "lightning"pattern shown in the other embodiments. The pattern consists of edges 98which extend radially and circumferentially and of edges 96 which extendgenerally circumferentially to join one end, e.g. the inner diameterend, of one edge 98 to the opposite end, e.g. the outer diameter end, ofthe next adjacent edge 96 of the same groove 90.

The circumferentially and radially extending edges 98 are disposed in ageneral direction which is convergent with the leading edge boundary 91.Each edge 98 preferably is neither parallel nor diverent to the edgeboundary 91, because divergent edges 91,98 would detract from theconstricting effect of the converging edges 96,98 and these effectswould undesirably tend to counteract each other. Reduction of volumeavailable to the fluid as it is being pumped from the circumferentialedge 88 inwardly along the sealing face 82 is important. The relativeangle γ, defined by the leading boundary edge 91 and the circumferentialedge 88, is larger as compared to the angle α defined by the same edgesin the embodiment of FIG. 1. An angle δ, formed by the trailing edges 98and the circumferential edge 88 is approximately equal or slightlygreater than the angle γ. Substantially equal angles would beconvergent, due to the circumferential displacement of the points on thecircumferential edge 88 about which the angles γ,δ are taken. Of course,an angle δ that is greater than the angle γ would provide moreconvergent triangulation toward an extrapolated intersection point 99,as is shown in FIG. 9.

Other adjustments to the shape of grooves 90 may be necessary toaccommodate the angle γ having a greater value For example, for an angleγ of approximately 30° it may be necessary to shorten or lengthen thearcs defining the generally circumferentially extending edges 96.

An important consideration in this regard is the "mass flow" orequalized fluid volume which is being pumped toward and over each of theterminal corners 94 relative to the other corners 94 of the same groove.Ideally, the mass flow which the groove 90 is directing toward eachterminal corner 94 is equal to that which is directed toward the othercorners 94. In this way, the amount of fluid, and the resulting pressurewhich is produced at each "pressure zone" is approximately equal withthat produced at the other terminal corners 94. Thus, general pressureparity or equalization across a number of discrete areas of the sealingface, and distribution of those areas over a broader radial area of thesealing face, provide for approximately equal lift characteristics ofeach pressure zone and approximately equal heat transfers at eachterminal corner 94 of each groove 90. Moreover, the capability ofdisposing a greater number of grooves along the grooved area 84 of theseal ring 80 distributes to a greater extent the mass flow over agreater number of terminal corners 94, thus further reducing theindividual pressure generated at each corner 94.

Pressure distribution across a greater area provides for furtherstabilization of the seal gap between the sealing faces because thegreater pressure zone area extends over a longer radial portion of theseal face. If viewed in cross-section, for example in FIG. 2, thepressure zone 25 which is closest to the circumferential edge 18 islocated at a position much farther removed from the centroid 100 of theseal ring 10. Separation of the pressure zone from the centroid 100provides for a larger moment arm about the centroid 100. The largermoment arm stabilizes the seal gap because it creates a more sensitiveand quicker responding negative feedback loop in which a correctiveforce acts on a seal ring to more quickly bring the sealing faces intoparallel alignment.

Other modifications are contemplated as being possible by those havingordinary skill in the art once an understanding of this invention ishad. For example, differences in the surface height of the grooves maybe made radially, as well as circumferentially, to provide a "stadium"pattern, the deepest groove sector being at the leading boundary of thegroove closest to the circumferential edge and increasing in height asthe groove depth is measured inwardly radially and alsocircumferentially. This would utilize the teachings of varying thegroove depth as taught by both the embodiments of FIGS. 3,4 and FIGS.5,6. Other modifications are also contemplated, such as changes in theangle made by the boundaries 21,23 and the circumferential edge 18.

Other changes, such as making the transverse portions 26 extend not onlycircumferentially, but also to a small extent, radially, are within thescope of the invention.

What is claimed is:
 1. A mechanical face seal for providing a sealbetween a pair of relatively rotatable components comprising a firstseal ring adapted to be mounted non-rotatably on one of said componentsand sealed with respect to said one component; a second seal ringadapted to be mounted non-rotatably on the other component and sealedwith respect to said other component, said second seal ring beingmounted in axial alignment with the first seal ring; and means beingprovided for resiliently urging an annular sealing face of the firstseal ring axially into sealing engagement with an annular sealing faceof the second seal ring; the sealing face of one of said seal ringshaving an annular grooved portion including a plurality of spaced apartgrooved areas disposed around its circumference, with said grooved areasopen to one circumferential edge of the sealing face, and a continuousannular dam provided between the grooved portion and the othercircumferential edge of said sealing face, the grooved portion and thedam being defined by a circumferential border, each said grooved areahaving:first and second spaced apart groove boundaries formed by grooveedges, said first groove boundary defining a first point of intersectionwith said circumferential edge of said sealing face to which saidgrooved areas open and said second groove boundary defining a secondpoint of intersection with said circumferential edge of said sealingface to which said grooved areas open, said first groove boundary andsaid second groove boundary having a point of intersection with saidcircumferential border, said groove edge of said second groove boundaryincluding at least two spaced apart groove edge portions, each saidgroove edge portion extending from a point of commencement radiallytoward said dam and circumferentially in a direction away from saidfirst point of intersection to a terminal point, said first grooveboundary extending from said first point of intersection radially towardsaid dam and circumferentially in a direction toward said second pointof intersection.
 2. The seal according to claim 1 wherein said point ofintersection of said circumferential border with said first grooveboundary is spaced from said point of intersection of saidcircumferential border with said second groove boundary, said respectivepoints of intersection of said first and second groove boundaries andsaid circumferential border are joined by a circumferentially extendinggroove edge which is coextensive with said circumferential border. 3.The seal according to claim 1 wherein said second point of intersectionis disposed circumferentially between said first point of intersectionand said point of intersection of said second boundary with saidcircumferential border.
 4. The seal according to claim 1 wherein saidterminal point of a spaced apart groove edge portion and the point ofcommencement of an adjacent one of said spaced apart groove edgeportions are joined by a circumferentially extending edge portion. 5.The seal according to claim 4 wherein each said spaced apart groove edgeportion closest to said circumferential border has a terminal pointwhich coincides with the point of intersection of said first grooveboundary with said circumferential border.
 6. The seal according toclaim 1 wherein said first groove boundary is a leading boundary andsaid second groove boundary is a trailing boundary, where leading andtrailing boundaries are defined with respect to the direction ofrelative rotation of the seal ring including said grooves in relation tothe opposing mating seal ring.
 7. The seal according to claim 1 whereinsaid first and second spaced apart groove boundaries intersect at acommon intersection point with said circumferential border.
 8. Amechanical face seal for providing a seal between a pair of relativelyrotatable components comprising a first seal ring adapted to be mountednon-rotatably on one of said components and sealed with respect to saidone component; a second seal ring adapted to be mounted non-rotatably onthe other component and sealed with respect to said other component,said second seal ring being mounted in axial alignment with the firstseal ring; and means being provided for resiliently urging an annularsealing face of the first seal ring axially into sealing engagement withan annular sealing face of the second seal ring; the sealing face of oneof said seal rings having an annular grooved portion including aplurality of spaced apart grooved areas disposed around itscircumference, with said grooved areas open to one circumferential edgeof the sealing face, and a continuous annular dam provided between thegrooved portion and the other circumferential edge of said sealing face,the grooved portion and the dam being defined by a circumferentialborder, each said grooved area having:first and second spaced apartgroove boundaries formed by groove edges, said first groove boundarydefining a first point of intersection with said circumferential edge ofsaid sealing face to which said grooved areas open and said secondgroove boundary defining a second point of intersection with saidcircumferential edge of said sealing face to which said grooved areasopen, said first groove boundary and said second groove boundary havinga point of intersection with said circumferential border, said secondpoint of intersection being disposed circumferentially between saidfirst point of intersection and said point of intersection of saidsecond boundary with said circumferential border, said groove edge ofsaid second groove boundary including at least two spaced apart grooveedge portions, each said groove edge portion extending from a point ofcommencement radially toward said dam to a terminal point, said firstgroove boundary extending from said first point of intersection radiallytoward said dam and circumferentially in a direction toward said secondpoint of intersection said second point of intersection being disposedcircumferentially between said first point of intersection and saidpoint of intersection of said second boundary with said circumferentialborder.
 9. The seal according to claim 8 wherein each of said at leasttwo spaced apart groove edge portions extend from said respective pointof commencement circumferentially in a direction away from said firstpoint of intersection.
 10. The seal according to claim 8 wherein saidpoint of intersection of said circumferential border with said firstgroove boundary is spaced from said point of intersection of saidcircumferential border with said second groove boundary, said respectivepoints of intersection of said first and second groove boundaries andsaid circumferential border being joined by a circumferentiallyextending groove edge which is coextensive with said circumferentialborder.
 11. The seal according to claim 8 wherein said first and secondspaced apart groove boundaries intersect at a common intersection pointwith said circumferential border.